1. Field of the Invention
This invention relates to an apparatus integrally having both image recognition function and image display function. More particularly, this invention relates to an apparatus having an active matrix type display functional device comprising a plurality of thin film transistors (TFT) that are arranged in matrix.
2. Description of the Related Art
Information processing apparatuses such as personal computers have become wide spread in recent years, and the demand for reading a variety of information as electronic information into the personal computers has been increasing. Therefore, a scanner has drawn an increasing attention as means for reading the information printed on sheets of paper, and so forth.
However, the scanner is independent as a peripheral device, and is not free from the problems that the operation is difficult and an appropriate storage place is not easy to find out.
Under such circumstances, a liquid crystal panel having a unitary structure of a color scanner and a touch system panel has been put into practical application. The construction will be hereby explained briefly. A color scanner using a line sensor is put on a liquid crystal panel. When the scanner is used, a document is placed on the screen. The line sensor is allowed to scan to read the document. Therefore, this liquid crystal panel needs a large area and a large capacity.
Recently, a TFT technology using a polycrystalline silicon called “poly-silicon TFT” has been examined intensively. As a result, it has become possible to fabricate a driving circuit having a shift register circuit, etc, by using the poly-silicon TFT, and an active matrix type liquid crystal panel having a pixel unit and a peripheral driving circuit for driving the pixel unit on the same substrate has been put into practical application. Consequently, the liquid crystal panel has become smaller in size and weight, and has been used for the display unit of a variety of information processing apparatuses and portable apparatuses such as personal computers, video cameras, digital cameras, and so forth. Moreover, the development of self-light-emission type display devices such as organic EL has been under way.
Compact portable information processing terminals (or “mobile computers”), that have higher portability and is more economical and smaller in size than the notebook type personal computers, have gained a wider application nowadays, and the active matrix type liquid crystal panel has been used mainly for the display unit. In such information processing terminals, data can be inputted from the display unit by a touch-pen system. To input printed information on sheets of paper such as character and picture information and video information, however, it becomes necessary to connect a peripheral device for reading the image such as a scanner or a digital camera to the information processing terminal. Therefore, portability of the information processing terminal is lost. Also, an economical burden is applied to the user to purchase such a peripheral device.
The active matrix type liquid crystal display device has also been used for the display unit of a TV conference system, a TV telephone system and an Internet terminal. Such systems and terminals include a camera (CCD camera) for taking the picture of the speaker or the user. However, the display unit and the read unit (sensor unit) are produced separately and individually and are modulated together. Therefore, the production cost is high.
In addition, the biggest feature of the portable information terminal is its portability. Therefore, the capacity of the portable information terminals is preferably as small as possible. Various attempts have been made to reduce the capacity by, for example, miniaturizing the components, but scale-down is practically limited to a certain level because the operation time provided by the cell unit as a power source cannot be sacrificed. It has thus been necessary not only to improve the cell but also to restrict power consumption of the terminal itself so as to reduce the capacity of the cell components and to secure a predetermined operation time.
It has been pointed out that the major proportion of this power consumption are occupied by the light source required for the liquid crystal display device.